1. Field of the Invention
The present invention relates to a control and/or regulating system of a machine for making a fibrous web, such as a paper and/or cardboard web. In particular, the present invention relates to the control of a machine having a plurality of actuators, each assigned to one final control element, for varying certain properties of the fibrous web to be made.
2. Description of Background Information
A known control and/or regulating system is disclosed in European Patent Disclosure EP-A 0 401 188. The known system has a conventional bus structure with a master and a plurality of slaves for communication between a higher-ranking control unit and the actuators for a cross-direction profile final control element. A characteristic of such a bus structure, which has long been used in many areas of industrial control, is that all the bus participants receive the commands of the master simultaneously. However, but normally only the addressed slave that has the correct address executes the corresponding command and then responds to the master.
A disadvantage of this prior art device is that with the exception of generalized addressing (broadcasting) in which all the slaves are addressed simultaneously, only one action can be performed at any particular time. With such a bus structure, it is impossible from the outset to use a plurality of masters, and thus for example there is no opportunity to use a plurality of control units on the principle of redundancy. An active redundancy concept, for instance with an automatic switchover in the case of a failure, is not a feasible option. Furthermore, the master must always call up the relevant status and alarm reports as well, which is very time-consuming. The number of bus participants is typically limited by bus drivers. A possibly contemplated embodiment with intrinsically desirable fiber-optic hardware would involve major difficulties and considerable expense. Another disadvantage is that hardware address coding is required for the individual participants.